Myocardial ischemia refers to a kind of pathological state that reduction of blood perfusion in heart causes reduced oxygen supply to heart, irregular energy metabolism of myocardium and abnormal work of heart. Clinical studies revealed that coronary artery stenosis, whose primary cause is arteriosclerosis, is the most major and common pathogenesis of myocardial ischemia. Coronary disease, what people often say, is heart disease caused by coronary atherosclerosis. At present, there are a lot of therapeutic regimes for myocardial ischemia which is a kind of coronary heart disease, such as stent placement and balloon dilation, whereas drug therapy is still a main method. Nitrate esters medicines (e.g. isosorbide mononitrate or its slow-release), beta blockers like propranolol and calcium channel blockers like nifedipine could be selected to dilate coronary arteries, increase myocardial oxygen supply, reduce peripheral resistance, working of heart and oxygen consumption of myocardium. Statins (e.g. atorvastatin, simvastatin) also should be taken to reduce plasma cholesterol and steady atherosclerotic plaque, preventing plaque from coming off to form thrombosis which causes stroke.
Inflammatory reaction plays important roles in the myocardial ischemia injury, whose main processes include the chemotaxis and infiltration of inflammatory-cells such as neutrophils, monocytes and lymphocytes etc., as well as the synthesis and secretion of inflammation factors. However, up till now, there is no clinical medicine for protecting myocardial ischemia by the anti-inflammatory mechanism. The monocyte locomotion inhibitory factor (MLIF), which is a polypeptide of anti-inflammatory reaction, is a pentapeptide found in sterile cultured amoeba histolytica, whose amino acid sequence is Met-Gln-Cys-Asn-Ser (SEQ ID NO:1). Experiment results in vitro and in vivo demonstrated that the pentapeptide MLIF inhibits the migration of human monocytes and polymorphonuclear neutrophils. Amoeba histolytica influences cytokines secretion, inhibits inflammation and escapes immune response of host by producing the anti-inflammatory polypeptide. It has been reported that the pentapeptide micromolecular not only directly affects inflammatory cells, but also influences the inflammatory reaction process by interfering inflammatory cytokines secretion. The MLIF also inhibits inflammation chemokines such as MIP-1α and MIP-1β, and represses inflammatory cytokines secretion like 1L-1β and TNF-α along with the corresponding receptor expression. In the study, the inventor found out that MLIF has the function of preventing and treating ischemic cerebrovascular disease, which has already applied for a patent application, e.g., CN 200810200610.0), but so far, there is no report about the function of the polypeptide in preventing and treating myocardial ischemia.